1. Field of the Invention
The present invention is related to a solid state semiconductor storage device with non-volatile memory, and more particularly to a solid state semiconductor storage device with temperature control function and a temperature controlling method thereof.
2. Description of Related Art
Solid state semiconductor storage devices become more and more popular. There are many applications utilizing solid state non-volatile memory to record digital information, such as USB flash drive, memory card, and solid state disk (SSD) drive. The solid state disk drive, which has the biggest capacity, is suitable to replace the hard disk drive in a portable computer (such as notebook, and ultra-mobile PC (UMPC)), so as to provide the properties of low power consumption, high storage speed and high reliability. For providing higher storage capacity and accessing speed, the solid state semiconductor storage device needs plural non-volatile memories, such that the operations of data access, recording and erasing can be performed at the same time, thereby reducing the operation time and therefore improving the accessing speed.
Please refer to FIG. 1, which is a block diagram showing the conventional solid state disk drive. The solid state disk drive 1 includes power managing unit 11, non-volatile memory unit 12 and control unit 13. The power managing unit 11 receives the power from the application system (not shown) and converts the power into a form suitable for other units inside the solid state disk drive. The control unit 13 connects to the system through the system interface for receiving commands and controls the non-volatile memory unit 12 to execute data input, data output, memory page write-in, memory block erasing and other necessary operations. Further, in the control unit 13, the system interface 131 is used to connect to the system, the memory interface 132 is used to connect to the non-volatile memory unit 12, and the microprocessor 133 executes the commands of the system and controls data transmission, the non-volatile memory unit 12 and data buffering in the data transmission buffer 134. The non-volatile memory unit 12 is constituted by at least one or more non-volatile memories, and it receives the control command from the control unit 13 so as to record digital information and provide thereof to the system.
U.S. Pat. No. 6,725,321 entitled “Memory system”, U.S. Pat. No. 6,718,406 entitled “Memory array apparatus with reduced data accessing time and method for the same”, and US Patent Application Publication No. 20050010717 entitled “Access and data management method using double parallel tracks for flash memory cells” provide the system architecture of solid state disk drive and method thereof. However, since inside the solid state disk drive there are many electronic elements operating at the same, they will produce much heat in the portable computer, and the increase in temperature may cause unstable operation.
FIG. 2 shows a conventional memory system with temperature control device for preventing unstable operation caused by temperature alteration. The memory system 300 includes a controller 310 and a memory device 320, wherein the controller 310 reads/writes the memory device 320 through a USB (Universal Serial Bus) 300. The controller 310 includes a track circuit 316 and a control circuit 315, wherein the track circuit 316 is used to monitor the operation of the memory device 320 in a particular duration, including the number of reading/writing or the number of updating. The control circuit 315 can decide the operation temperature of the memory device 320 in the particular duration according to the information provided by the track circuit 316, which monitors the operation of the memory device 320, and the former operation information of the memory device 320. Then, if the control circuit 315 decides that the operation temperature of the memory device 320 has exceeded the tolerant range, it will modulate the memory device 320 for reducing the operation temperature by inserting a delay time between read/write operations, or by switching the memory device 320 to a low power mode.
However, the technology described above is only suitable for volatile memory whose heat dispersing is related to the read/write speed of the memory controller as accessing the memory. Since the solid state disk drive adopts non-volatile memory (such as NAND type flash memory) for long-term data storage, the access process and characteristics thereof are quite different from volatile memory. For example, the difference of NAND type flash memory, which is adopted by the current solid state disk drive, from volatile RAM are:
1. The data stored in the NAND-type flash memory can not be randomly accessed, and the access operation should be executed through the instruction code and also has a designated procedure that the access size is larger, such as memory page or memory block.
2. The NAND-type flash memory, except the common data input/output operation like the volatile RAM, further needs to write in memory page or erase memory block for completing data recording.
3. The power consumption is much higher, since the NAND-type flash memory needs more time to execute memory page write-in or memory block erasing, and thus, the produced heat is also higher.
According to the differences, it is known that NAND-type flash memory has different characteristics from the volatile RAM, so that the above-described temperature control technology is not suitable for the solid state disk drive or other solid state semiconductor storage device. Therefore, there still exists the need to solve the problem of unstable operation caused by high temperature in the solid state semiconductor storage device.